Self-sharpening pencil.



N. CRANE.

SELF SHARPENING PENCIL.

APPLICATION FILED SEPT 13, 1911,

1,038,857,, Patented Sept. 17, 1912.

' Wrrnn STATES PATENT OFFICE.

NEWTON CRANE, OF BOSTON, IIIASSACHUSETTS, ASSIGNOB, BY MESNE ASSIGNMENTS, TO SELF-SHARPENING PENCIL COMPANY, OF PROVIDENCE, RHODE ISLAND, A

CORPORATION OF RHODE ISLAND.

SELF-SHARIENING PENCIL.

Specification of Letters Patent.

Patented Sept. 1 7,1912.

Application filed September 13,1911. Serial No. 649,143.

T all whom it may concern:

Be it .known that I, NEWTON CRANE, of Boston, in the county of Suffolk and State of Massachusetts, have invented certain new proved means" for propelling the lead of the pencil asthesamebecom'es worn away, of

such a character as to simplify and reduce the cost of theconstruction of the pencil.

The preferred manner in which I secure the objects above indicated is described in detail in the 'following specificatlon and 1s illustrated in the accompanying drawings, in which, v

' Figure 1 represents a perspective view of the pencil. Fig. 2 is a side elevation of the same, showi the actual size thereof. F g. 3 is a longitu i'rial section showing the entire pencil on an enlarged scale, Fig. 4 1s a right-hand. end View of Fig. 3. Fig. 5 is an elevation of the propelling mechanism. Fig. 6 is a longitudinal section of the compound 1 ropeller screw and magazine for leads.

igs. 7 and 8 are sectional views on lines 77 and 8-8 res ectively of Fig. 3. F g. 9 is a side view 0 the lead propeller. Flg. 10 is a perspective view of the lead guide and friction retainer for the lead. Fig. 11 is a perspective view greatly enlarged of a lead used in the pencil. Fig. 12 is a similar view showin the manner in which facets are formed in the corners of the lead by wear. .Fig. 13 represents an. end view of a modified form of lead.

The same reference characters indicate the same parts in all the figures.

Referring to the drawings (1 represents the case of the pencil which is conveniently a metallic shell, although it may be of any other material. This case has approximately the same ro ortions and dimensions as the ordinary lira pencils of commerce, but dif- :fers therefrom in that it is given wholly or in part a rismatic form. At one end the walls of t e case converge to correspond with the pointed end of the ordinary lead pencil, and to avoid abrupt transverse projections adjacent to the marking point.

1) represents a guide for the lead, which is preferably a tube of approximately the same shape and area in-cross section as the lead, and is located in the longitudinal axis of the case, one end being contained in the small end of the case, to which it is united in any way suitable for giving suiiicient strength, as by solder at c.

0! represents a pusher of which one end enters the guide tube In and bears against theinner end of the lead 6, which latter nor.- mally protrudes from the end of the tube and also the small end of the case.

f represents a combined propeller for the pusher d and magazine for leads, and it is preferably formed as a tube extending into the case from the large end thereof and having a helical groove 9 corresponding to a screw thread which is engaged by the helically bent end 0! of the pusher. The propeller f is swiveled in the case, being rotatably'inounted in a plate h which fits in the open large end of the case and is retained therein by means of solder or in any other desired way. There is an almost endless variety of ways in which such plate may be secured and that described is merely illustrative of one of these many ways. A. plug or cap 71 having a head 2" passes through theopen end of'the propeller tube f and serves both as a cover for such tube and as the mechanical element on which force for rotating the tube may be applied. The stem of the cover is notched at 9' so as to form jaws or prongs which embrace a projection 70 on the interior of the propeller tube to provide a non-rotating engagement therewith.v The head i is accessible to the fingers of the user of the pencil, who can thus rasp and turn the head withthe thumb an finger of one hand while holding the encil case in the other, and thereby turn t e propeller so as to advance the pusher and free the lead.

The foregoing is a general description of the main parts of the pencil. I will now proceed to describe the form, construction and principles of the several parts more minutely and in detail.

The most important feature of the invention resides in the character of the lead by virtue of which it is enabled always to pre,

.sent a sharp point ready for use, no matter how much it may have been worn by use.

' with sharp corners. It is also comparatively small in cross sectional area. As 'will be readily understood, when the lead is cut or broken with its end erpendicular to its length, the corners o the prism provide 7 three sharp points, eachcapable of making a fine line. In using the pencil itwill be so held that one of the pointsfbears upon the paper. "Asthis point wears, away it forms afacet of which the boundaries as wear progresses gradually approach the other two corners or'angles of the prism. When the surface produced by such wear is too wide to give a fine line, the pencil may be turned to present a fresh pointtothe paper. Each of the corners in wearing away reduces the amount of material adjacent to the other two corners. and thus sharpens the points at these corners. Thus thewearing away of'each-corner forms a side which approaches the other corners and reduces the cross sectional area of the lead at the end. Whenever twoor moreof the corners are worn .away so far that the facets produced by wear intersect, such intersec ion produces a new shar point.

' B y ma ng the lead sufiicientl small in Y cross sectional area it is impos'si Is for the lead to wear far enough to make an objec- .tionably broad line before it brin s down the adjacent parts oi the lead to a su 'ciently fine-point. ,Thus during the attrition at any one part of the leadln the ordinary use thereof, adjacent parts are being brought Into a sufficiently pointed condition to be satisfactorily used.

The lead is prevented'from turning in the, pencil and so held in its relation to the paper by the tube b, which is likewise prismatic and is of approximately the same shape and sizeas the lead. Conveniently thistube is made of a strip of sheet metal of the proper width, bent up'along arallel lines until the opposite edges meet. at issomade asijto retain the lead fri'c'tionallyagainst drhpping out, and to secure thisfend may conveniently be provided with a tongue b' formed integrally'in one of the sides of the tube and bent inward so as to bear on the lead. The same effect may also be secured b itwistingthe tube sli htly about its longitu inal axisfi Another eature of the pencil is that thegasea is likewise prismatic,

aving theg same number of sides as the lead,

' which sides are so dis osed with relation to the side'sof the lead-t at when the pencil is held in the users hand in the natural positionforwriting, one of the sides bears on the users finger and holds the pencil in such a position that one of the angles of the lead is presented to the paper. I

' he propelling and magazine tube f is .the helical part to surround the lead, 1 I

conveniently made of a section of metallic tubing of which the inner end is spun over at f to provide a bottom capable of retaining theleads. In the sides of the tube is rolled the helical groove 9 which forms the thread, and near the outer or open end is' rolled an external bead f which forms a shoulder against which the plate It seats. The latter, of course has a perforation in its center which receives the mouth of the tube f, and the rim of this mouth is flanged over at f outside of the plate to retain the latter.. Thusa sufliciently firm coupling is afi'orded between the tube and plate by a means which costs yery little, and at the same time the tube is'swiveled. The projection previously mentioned may be formed as an inte ral part of'the tube 05:- 4

of great practical importance in that it enables a very sim 1e and inexpensive constructionto be utilized in the pencil, relates to the form of the pusher d. .Such pusher is offset at d between thehelicallybent end and the pushing end. Such ofiset enables ropeller tube, and at the same. timecauses' t e pushin part to lie in axial alinement with such tuhe and'gto enter the guide tube b,'which likewise .is-central in the case. Furthermore the oifset d lies within one of the dihedral angles of the case and prevents thepusher from turning with the propeller. Thus the shapeof the pencilis made to serve the additional end of holding the pusher from ro- [tation and compelling the rotation of the propeller, tube to give a direct endwise mo- 'tion to the'pusher, and avoiding the necessity ofemployi'ng more or less elaborate devices such as have been found essential in Fp'ropellingpencils hitherto for a like purpose.

' I-wish to make it understood that, althou h I have referred to m invention as relatmg to lead pencils, and ave described the markin element of such a pencil as a o; not thereby intend to limit m self to the useof black lead or graphite, w ich is ordinarily understood bythe term lead as here used. On the contrary I have used the term generically as meaning any solid substance capable of, being used in or as a pencil or crayon for producing a.

mark by attrition, and the following claims such, term wherever it is used is to be understood as meaning any substance or material of this character. I

The term prismatic which I have used in describing the shape of the pencil lead is not to be understood as limiting me to the use the leads formed exactly as geometrical prisms, that. is havin plane sides. It is within the contemplatlon of my invention to form the lead with concave sides, as'i'ndicated in Fig. 13, so that each of the di- 4 set inwardly. A eature which is likewise hedral' angles or corners of the lead form ribs sharper than the dihedral an les of a true prism. It will be very rea ily seen that this formation'diminishes the possible area of a facet produced by wear, thus keeping the lead sharp for a longer period and increasing its self-sharpening quality." The number of sides ofthe prismatic lead and the number of corners or ribs formed between the plane or concave sides of such ribs is limited by the necessity of allowing only one such corner or rib to bear on the paper at the same time, and of causing other corners to be sharpened while one corner is wearing away. Thus the lead will not generally be iven more than four sides, while; a three-Si ed lead is best; 7 v

I claim 1. A pencil consisting of a substantially prismatic lead, each of the angles of which is sharper than a right angle, and a case having flattened finger-engaging portions substantially parallel to the several sides vof the lead.

2. A'pencil consisting of a casing and a.

lead, each having substantially the form of an equilateral triangular prism, arranged with corresponding sides respectively sub stantially parallel, whereby grasping of the casing in any position suitable for use causes one of the angles of the leadto be directed toward the marking surface.

In testimony whereofI have aflixed my signature, in presence of two witnesses.

' NEWTON CRANE.

Witnesses:

ABTHUB'H- Brown, P. W. Pnzznrrx. 

